Drainage systems for conducting away surface water collected from a large area, such as a pedestrian zone and comparable areas for parking cars, underground garages and so on are already known. For such large areas linear drainage systems are used, in which a set of individual channels lined up in a row are buried in the ground and the openings at the tops of the channels are covered with gratings shaped in various ways and made of diverse materials. However, it is becoming increasingly common to pave areas of this kind not with concrete or asphalt but rather with paving stones or hollow blocks. The presence of grating-type drain covers impairs the aesthetic effect of the pattern of paving stones, and the appearance of the area to be drained is disrupted by the contours of the drainage system.
In order to achieve an inconspicuous drainage of paved areas, drainage channels are provided with specially constructed frames on which standard shaped stones are placed and kept in position in such a way that an opening in the form of a slot is left between the shaped stones. Through this slot the surface runoff can enter the drainage channels. Disadvantages of such drainage systems are on one hand the need for frames, which much be matched to the size of the particular paving stones or hollow blocks being used, and on the other hand the difficulty of fitting the frames to the channels when the area is being paved.
The German patent DE 42 37 237 A1 discloses a cover element for a drainage channel that consists of two longitudinally extending L-shaped parts in opposite orientations, each of which comprises an upright section and a section so shaped that it partially covers the drainage channel; the arrangement is such that the adjacent upright sections define between them a slot through which the surface runoff can flow into the drainage channel. This drainage system is both simple to construct and usable with every size or color of paving stones or hollow blocks.
When a separating or sealing layer is provided below the pavement, to ensure that water percolating through the pavement is prevented from entering underground structures such as a parking garage, this percolating water must be conducted away through many separate, punctate drainage holes, which is complicated and expensive.